Wednesday, June 01, 2011

“Representational rigidity” in our aging brains

Great...here we have Yassa et al. showing how a portion of the brain is doing what my knee joints are slowing doing, becoming more rigid with age. They look at the "place cells" in the hippocampus thought to be involved with discriminating between similar patterns. Long-term memory functions deteriorate with age, and the hippocampus, which play a role in learning new facts and remembering events, is one the sites that undergo the earliest changes.

Converging data from rodents and humans have demonstrated an age-related decline in pattern separation abilities (the ability to discriminate among similar experiences). Several studies have proposed the dentate and CA3 subfields of the hippocampus as the potential locus of this change. Specifically, these studies identified rigidity in place cell remapping in similar environments in the CA3. We used high-resolution fMRI to examine activity profiles in the dentate gyrus and CA3 in young and older adults as stimulus similarity was incrementally varied. We report evidence for “representational rigidity” in older adults’ dentate/CA3 that is linked to behavioral discrimination deficits. Using ultrahigh-resolution diffusion imaging, we quantified both the integrity of the perforant path as well as dentate/CA3 dendritic changes and found that both were correlated with dentate/CA3 functional rigidity. These results highlight structural and functional alterations in the hippocampal network that predict age-related changes in memory function and present potential targets for intervention.